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fix(sqlalchemy-spanner): support spanner_storing in Alembic op.create_index() and compare_indexes() - #18840
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fix(sqlalchemy-spanner): support spanner_storing in Alembic op.create_index() and compare_indexes()#18840rocksnow1942 wants to merge 2 commits into
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…_index() and compare_indexes()
1. In SpannerDDLCompiler.visit_create_index, support string column names
in spanner_storing without requiring them in index.table.c. When Alembic
executes op.create_index(), the dummy Table only contains the indexed
key columns; looking up storing columns in index.table.c raises KeyError.
2. Register SpannerImpl subclassing alembic.ddl.impl.DefaultImpl for
dialect 'spanner+spanner' when Alembic is installed:
- Override compare_indexes to compare spanner_storing as sets,
avoiding spurious autogenerate diffs when reflected columns
are reordered.
- Override create_index to ensure string storing columns are appended
to index.table.c as NullType columns if missing.
Fixes googleapis#18835
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This pull request introduces Alembic DDL support for Google Cloud Spanner, specifically implementing index comparison and creation with STORING columns. It adds SpannerImpl (inheriting from Alembic's DefaultImpl) to handle comparing indexes with storing columns and dynamically appending missing storing columns to the table schema during index creation. Unit tests are added to verify these behaviors and edge cases. Feedback was provided to simplify column name extraction in SpannerImpl.create_index by directly accessing col.name instead of using getattr, ensuring consistency with other parts of the codebase.
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Fixes #18835 🦕
Summary
This PR resolves two issues when using
sa.Index(..., spanner_storing=[...])with Alembic:op.create_index(..., spanner_storing=["col"])raisingKeyErroron string column names:op.create_index("ix", "tbl", ["c1"], spanner_storing=["c2"])runs inside an Alembic migration,alembic.operations.schemaobj.SchemaObjects.indexconstructs an ad-hocTable("tbl")containing only the indexed key columns (["c1"]).SpannerDDLCompiler.visit_create_indexpreviously resolved string column names viaindex.table.c[col], raisingKeyError: 'c2'. It now extracts the column name directly (c if isinstance(c, str) else c.name).SpannerImpl.create_indexappends missing storing columns toindex.table.casNullTypecolumns (matching Alembic'sPostgresqlImpl.create_indexandMSSQLImpl.create_index).Alembic
--autogenerateignoringspanner_storingchanges:SpannerImpl(DefaultImpl)for"spanner+spanner"when Alembic is installed, overridingcompare_indexesto comparespanner_storingcolumn sets (set(m_storing) != set(r_storing)). Comparing as sets detects additions, removals, and modifications ofSTORINGcolumns while avoiding false-positive diffs when Spanner reflection returnsSTORINGcolumns in table-column order.